During the last decade, lisianthus (Eustoma grandiflorum) has been introduced in Iran in the horticultural cut-flower industry. This crop is currently produced in more than 800 small greenhouses on a surface of an estimated 0.8 km2 in the Pakdasht region (southeast of Teheran Province). Plants exhibiting virus-like symptoms were observed in several greenhouses in 2010. The infected plants produced yellow and necrotic spots on the leaves and became severely deformed because of a strong leaf curling and the production of shorter internodes. Flower breaking has not been observed in the blue flowering plants. Approximately 85% of the plants were apparently infected in the inspected greenhouses. Extracts of infected material inoculated onto some indicator plant species induced mosaic and leaf malformation on Nicotiana benthamiana, mottling on Capsicum annuum, necrotic lesions on Datura stramonium, chlorotic local spots on Vigna unguiculata, systemic necrotic spots on Emilia sonchifolia, chlorotic local spots on Cucumis sativus, and necrotic local lesions on Petunia hybrida. Back-inoculation of infected material on lisianthus seedlings resulted in several chlorotic spots on the inoculated leaves and a severe downward curling of the systemic infected leaves. No symptoms were observed after inoculation of Pisum sativum, Phaseolus vulgaris, Vicia faba, and Chrysanthemum spp. The virus could also be transferred from infected to healthy N. benthamiana plants by pricking leaves with a Pasteur pipette. Spherical tombusvirus-like particles of approximately 29 nm were found by transmission electron microscopy in leaf-dip and partially-purified preparations of infected N. benthamiana. Since Tomato bushy stunt virus (TBSV; genus Tombusvirus, family Tombusviridae) and Moroccan pepper virus (MPV) have been found in Iran, we studied by using ELISA whether our samples matched with TBSV. Since a negative response was obtained, two primers were designed on the basis of the available sequences of the coat protein in the GenBank (Accession No. EU27780) of an MPV isolate from soil in Fars Province, Iran. A reverse transcription (RT)-PCR of total RNA extract from infected lisianthus and N. benthamiana with the primers MPV-R (5'-TTACAACAATGTGGCATCATTG-3') and MPV-F (5'-ATGGCAATGGTAGTAAG AAAC-3') resulted in a DNA fragment of 1,176 bp. This fragment from N. benthamiana was cloned, sequenced (Accession No. HQ663881), and showed a 96% nucleotide and 99% amino acid identity with the coat protein of the soil isolate. MPV was originally found in pepper (1), tomato and pelargonium (4), pear tree (3), and surface water (2). To our knowledge, this is the first report of MPV on lisianthus in Iran and worldwide. This virus, which persists in soil, water, and plant debris, can be considered as a substantial threat for the lisianthus industry in Iran because farmers do not apply strict crop rotation or other sanitation measures